Hydration of Alkaline Earth Metal Dications: Effects of Metal Ion Size Determined Using Infrared Action Spectroscopy
- 1 September 2009
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 131 (37), 13270-13277
- https://doi.org/10.1021/ja901011x
Abstract
Infrared laser action spectroscopy is used to characterize divalent Mg, Ca, and Ba ions solvated by discrete numbers of water molecules in the gas phase. The spectra of the hexahydrated ions are very similar and indicate that all six water molecules directly solvate the metal ion. The spectra of the heptahydrated ions indicate the presence of populations of structures that have a water molecule in the outer shell for all ions and an average coordination number (CN) for Ba that is higher than that for Ca or Mg. Comparisons between CN values obtained from M06 density functional and local MP2 theory indicate that the B3LYP density functional favors smaller CN values. The spectra of clusters containing at least 12 water molecules indicate that the relative abundance of single-acceptor water molecules for a given cluster size decreases with increasing metal ion size, indicating that tighter water binding to smaller metal ions disrupts the hydrogen bond network and results in fewer net hydrogen bonds. The spectra of the largest clusters (n = 32) are very similar, suggesting that intrinsic water properties are more important than ion−water interactions by that size, but subtle effects of Mg on surface water molecules are observed even for such large cluster sizes.Keywords
This publication has 69 references indexed in Scilit:
- Hydration of Gaseous Copper Dications Probed by IR Action SpectroscopyThe Journal of Physical Chemistry A, 2008
- Hydration of the Calcium Dication: Direct Evidence for Second Shell Formation from Infrared SpectroscopyChemphyschem, 2007
- Binding energies for the inner hydration shells of Ca2+: An experimental and theoretical investigation of Ca2+(H2O)x complexes (x=5–9)International Journal of Mass Spectrometry, 2007
- Mimicking solvent shells in the gas phase. II. Solvation of K+The Journal of Chemical Physics, 2006
- Infrared Spectroscopy of Hydrated Amino Acids in the Gas Phase: Protonated and Lithiated ValineJournal of the American Chemical Society, 2005
- Solvation Dynamics in Ni+(H2O)nClusters Probed with Infrared SpectroscopyJournal of the American Chemical Society, 2005
- Infrared Photodissociation Spectroscopy of [Mg·(H2O)1-4]+ and [Mg·(H2O)1-4·Ar]+The Journal of Physical Chemistry A, 2004
- Molecular Aspects of Halide Ion Hydration: The Cluster ApproachAnnual Review of Physical Chemistry, 2003
- Hydration Energies and Structures of Alkaline Earth Metal Ions, M2+(H2O)n, n = 5−7, M = Mg, Ca, Sr, and BaJournal of the American Chemical Society, 1999
- Hydration Energies and Entropies for Mg2+, Ca2+, Sr2+, and Ba2+ from Gas-Phase Ion−Water Molecule Equilibria DeterminationsThe Journal of Physical Chemistry A, 1998